Process and apparatus for the orientation of the stable direction of magnetization of a magnetic layer carried by a cylindrical support

ABSTRACT

A process and corresponding apparatus providing for obtaining circumferential orientation of the stable axis of magnetization in a magnetic layer during deposition of the layer on a cylindrical support. This arrangement includes flat windings positioned in parallel to the support and being traversed by polyphase currents and furnishing magnetic field orthozonal to the axis of the support and rotating around the same.

United States Patent Girard et al'.

[54] PROCESS AND APPARATUS FOR THE ORIENTATION OF THE STABLE DIRECTION OF MAGNETIZATION OF A MAGNETIC LAYER CARRIED BY A CYLINDRICAL SUPPORT [72] Inventors: Rene Fernand Victor -Girard, Grenobel; Jacques be Guillerm, Avrille, both of France a v [73] Assignee: Societe Industrielle Honeywell Bull, Paris,

France 22 Filed: Apr.2l, 1970 21 Appl. No.: 30,479

[30] Foreign Application Priority Data Apr. 25, 1969 France, ..6913136 1.11011 1/00 581 Field of Search ..335/284, 209, 232; 204/193, 204/206 1 Feb. 22, 1972 [56] References Cited UNITED STATES PATENTS 2,881,387 4/1959 Wood ..335/284 2,652,925 9/1953 Vermeiren. ..335/284 3,021,230 2/ 1962 Deriaud ..335/284 3,370,258

2/ l 968 Williams ..335/284 Primary Examiner-J. D. Miller Assistant ExaminerR. Skudy Attorney-George V. Eltgroth, Lewis P. Elbinger, Frank L. Neuhauser, Oscar B. Waddell and Joseph B, Forman [57] ABSTRACT A process and corresponding apparatus providing for obtaining circumferential orientation of the stable axis of magnetization in a magnetic layer during deposition of the layer on a cylindrical support. This arrangement includes flat windings positioned in parallel to the support and being traversed by polyphase currents and furnishing magnetic field orthozonal to the axis of the support and rotating around the same.

9 Claims, 3 Drawing Figures BACKGROUND OF THE INVENTION This invention relates to providing a stable axis of magnetization in a magnetic layer on a support and, more particularly, to a method and device for providing anisotropic circumferential orientation of a magnetic layer on a conductive cylindrical support.

It is known, that at the time of depositing a magnetic layer on a conductive cylindrical support, for example a wire, it is possible to orient the stable axis of magnetization in such layer perpendicularly to the axis of the support (circumferential direction), by providing for an electric current to traverse the support wire. The current traversing the support wire creates at the surface of the wire a circumferential magnetic field, whereby the magnetic layer acquires a circumferential anistropy of orientation, i.e., its stable axis of magnetization or of easy magnetization is circular and coaxial to the support wire. However, this method of circumferential orientation has limitations due especially to the heating of the support wire and, in the case where the deposition of the magnetic layer is provided by electrolysis and the support wire serves as the electrode, to the allowable drop of potential along such support wire. Thus, when a compound of iron and of nickel is deposited by electrolysis on a copper wire of beryllium of I25 microns diameter, the orienting field is limited to about ocrsteds, which is insufficient for a good orientation of the magnetization. Moreover, the maximum possible value of the orienting field is less as the diameter of the wire is reduced.

It is known, further, that to orient such a magnetic layer axially along its support, a field of orientation parallel to the axis of the support wire can be created in such magnetic layer by a magnetic or electromagnetic device disposed external to the support, such as by a solenoid.

The object of the present invention is to provide a process and apparatus for circumferentially orienting the stable axis of magnetization of a magnetic layer carried by a cylindrical support and to remedy the disadvantages of the prior art.

SUMMARY OF THE INVENTION In accordance with the invention, the process providing for the circumferential orientation of a stable axis of magnetization in a magnetic layer carried by a cylindrical support wire is characterized in that the magnetic layer is subjected to a magnetic field orthogonal to the axis of the support and rotated around the axis, such magnetic field being furnished by a device external to the wire.

Preferentially, the rotating-magnetic field is furnished by an arrangement of flat windings, wherein the winding planes are parallel to the cylindrical support wire and are traversed by polyphase current.

The arrangement may comprise n windings whose planes pass through the support wire and make between adjacent winding pairs angles equal to 17/71, these windings being traversed by currents ofn phases.

Preferably, the arrangement comprises 2m windings arranged in parallel pairs regularly disposed around the wire, two parallel windings being traversed by a current of the same phase, whereas all of the pairs of parallel windings are traversed by currents of m phases. It is particularly simple and advantageous if n=m=2.

In a preferred embodiment each of the windings has a rectangular form and consists of two sides parallel to the cylindrical support.

BRIEF DESCRIPTION OF DRAWING The invention will be described with reference to the accompanying drawing, wherein:

FIG. I is a perspective view of one embodiment for implemcnting the process ofthe invention;

FIG. 2 is a perspective view of another embodiment for implementing the process of the invention; and

FIG. 3 illustrates schematically the principle of the process of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT The embodiment of FIG. 1 comprises an electrolysis tank 1 containing, for example, an electrolyte with a base of iron and nickel. A copper wire 2 continuously traverses tank 1 from one end to the other and is covered during its passage through the tank with a magnetic layer 3.

In order to circumferentially orient the axis of magnetization of layer 3, tank 1 is enclosed by two windings 4 and 5 or rectangular form, whose planes pass through wire 2. Moreover, the planes of windings 4 and 5 are orthogonal. Windings 4 and 5 are supplied, at terminals 6, 7 and 8, 9 respectively, with two-phase currents.

The embodiment of FIG. 2 similarly comprises an electrolysis tank 1 traversed by wire 2. The tank of FIG. 2 is enclosed by four windings l013 of rectangular form, whose planes are parallel to wire 2. The planes of windings 10 and 12 are parallel and similarly the planes of windings 11 and 13 are parallel. Moreover, the lanes of windings l0 and 12 are orthogonal to those of windings l 1 and 13.

Windings l0 and 12 are supplied from the same terminals 14 and 15, and windings 11 and I3 are supplied from the same terminals 16 and 17. These terminals, in turn, are supplied with two-phase currents.

Thus, the magnetic field H furnished by windings 4 and 5 or by windings 10-13 is a field orthogonal to wire 2 and rotating around the wire.

At the instant shown in FIG. 3 the field H has a direction D and, therefore, the layer in the course of its deposition is circumferentially oriented according to the direction of saturation d, except at the points where the projection of the field H on a plane tangent to wire 2 is small and where it induces a north pole N and a south pole S.

However, the field H rotates around wire 2, so that the magnetic poles N and S are constantly moving. Therefore, layer 3 is correctly oriented at all points on its circumference.

Experience has proven that under conditions wherein the magnetic field H has a sufficient amplitude (at least equal to 10 oersteds) and wherein the frequency of the currents generating the field is of the order of 50 Hz., the angular dispersion of the material of layer 3 is less than 0.2 for a duration of deposition of some tens of seconds.

The process of the instant invention does not introduce an ohmic drop in cylindrical support 2, as does an orienting current. Under the instant conditions, the electric potential presented by wire 2 in electrolysis tank 1, in which the magnetic deposit is effected, is the same at all points along the wire, which is indispensible for obtaining on wire 2 a homogeneous distribution of current all along the tank.

This permits the utilization of electrolytes for which the composition of the deposit depends on the current density without introducing, through the intermediary of an inhomogeneity of current density along the wire in movement at the time of deposition, an inhomogeneity of composition in the thickness of the finished magnetic deposit.

Nevertheless, wire 2 is traversed by the continuous electrolysis current during the orientation of the magnetic layer 3 and, therefore, is subjected to a force perpendicular to thewire resulting from the action of alternating magnetic field H on this continuous current. Therefore, if wire 2 is subjected to a mechanical tension it vibrates under the action of this force, which perturbs the deposition of the magnetic layer.

For remedying this disadvantage, it is possible to reduce the span of wire 2 to the interior of tank 1, where the employment of the device permits pulling a wire through the tank under very low mechanical tension, such as described in French Pat. application No. P.V. N. 6, 910,210, filed Apr. 3, 1969, and in the corresponding US. Pat. application, Ser. No. 24,635, filed Apr. 1, 1970, by R. F. V. Girard and J. LeGuillerm, for Process And Apparatus For Obtaining Of Wires For Magnetic Memories, such applications being assigned to the assignee of the instant application.

Although the process of orientation of a stable axis of magnetization in a magnetic layer has been described for use in the deposition of a layer by electrolysis, it is apparent that this process can be employed for layers deposited by other means or already deposited on a support.

It can be seen that modifications can be made to the embodiments which have been described, particularly through the substitution of equivalent technical means, without departing from the heart of the present invention.

We claim:

1. A process providing for circumferentially orienting the stable axis of magnetization of a magnetic layer carried on a cylindrical support, wherein the improvement comprises: subjecting said layer to a magnetic field orthogonal to the axis of said support and rotating said field around said support axis, said magnetic field being provided by a device external to said support.

2. Apparatus providing for circumferentially orienting the.

stable axis of magnetization of a magnetic layer carried on a cylindrical support, wherein the improvement comprises: an arrangement offlat windings, the planes ofsaid windings being parallel to said support and being traversed by polyphase currents, said arrangement furnishing a magnetic field orthogonal to the axis of said support and rotating around said support axis.

3. The apparatus of claim 2, wherein said arrangement of windings comprises n windings the lanes of said windings passing through said wire and making between adjacent winding pairs angles equal to 11/11, said windings being traversed by currents of n phases.

4. The apparatus of claim 2, wherein said arrangement comprises 2m windings arranged in parallel pairs regularly disposed around said support, two parallel windings being traversed by a current of the same phase, all of said pairs of parallel windings are traversed by the currents of m phases.

5. The apparatus of claim 3, wherein said arrangement comprises two fiat windings having their planes orthogonal and being supplied by two-phase currents.

6. The apparatus of claim 4, wherein said arrangement comprises four windings arranged in parallel pairs surrounding said support, two parallel windings being traversed by a current of the same phase, wherein both pairs of parallel windings are supplied by two-phase currents.

7. The apparatus of claim 2, wherein each of said windings is of rectangular form and comprises two sides parallel to said cylindrical support.

8. The apparatus of claim 6, wherein each of said windings is of rectangular form and comprises two sides parallel to said cylindrical support.

9. Apparatus for providing circumferential magnetic orientation in a magnetic layer on a cylindrical support, comprising: a magnetic member disposed proximate said support for providing a magnetic field directed orthogonal'to the axis of said support, and means for controlling said magnetic member for rotating said field around said support axis. 

1. A process providing for circumferentially orienting the stable axis of magnetization of a magnetic layer carried on a cylindrical support, wherein the improvement comprises: subjecting said layer to a magnetic field orthogonal to the axis of said support and rotating said field around said support axis, said magnetic field being provided by a device external to said support.
 2. Apparatus providing for circumferentially orienting the stable axis of magnetization of a magnetic layer carried on a cylindrical support, wherein the improvement comprises: an arrangement of flat windings, the planes of said windings being parallel to said support and being traversed by polyphase currents, said arrangement furnishing a magnetic field orthogonal to the axis of said support and rotating around said support axis.
 3. The apparatus of claim 2, wherein said arrangement of windings comprises n windings the lanes of said windings passing through said wire and making between adjacent winding pairs angles equal to pi /n, said windings being traversed by currents of n phases.
 4. The apparatus of claim 2, wherein said arrangement comprises 2m windings arranged in parallel pairs regularly disposed around said support, two parallel windings being traversed by a current of the same phase, all of said pairs of parallel windings are traversed by the currents of m phases.
 5. The apparatus of claim 3, wherein said arrangement comprises two flat windings having their planes orthogonal and being supplied by two-phase currents.
 6. The apparatus of claim 4, wherein said arrangement comprises four windings arranged in parallel pairs surrounding said support, two parallel windings being traversed by a current of the same phase, wherein both pairs of parallel windings are supplied by two-phase currents.
 7. The apparatus of claim 2, wherein each of said windings is of rectangular form and comprises two sides parallel to said cylindrical support.
 8. The apparatus of claim 6, wherein each of said windings is of rectangular form and comprises two sides parallel to said cylindrical support.
 9. Apparatus for providing circumferential magnetic orientaTion in a magnetic layer on a cylindrical support, comprising: a magnetic member disposed proximate said support for providing a magnetic field directed orthogonal to the axis of said support, and means for controlling said magnetic member for rotating said field around said support axis. 